Preparation of SnS quantum dots for solar cells application by an in-situ solution chemical reaction process

SnS quantum dots (QDs) with size of 8 nm were synthesized by an in-situ room temperature solution chemical reaction process. Stannous chloride, as Sn precursor, was coated on the TiO₂ photo-anodes to form a solid precursor film. Ammonium sulfide was dissolved into ethanol to form anionic reaction solution. SnS quantum dots were generated by immersing the Sn-coated TiO₂ photo-anodes into the anionic solution. The structure, morphology and optical absorption properties of the SnS/TiO₂ photoanodes were investigated by means of XRD, SEM, TEM and UV–vis measurements. The photovoltaic properties of the SnS QDs sensitized TiO₂ solar cells were optimized by changing the number of deposition cycles of the SnS QDs. It turns out that the SnS/TiO₂ solar cell with 20 deposition cycles exhibited the best photovoltaic performance with an open-circuit voltage V_oc of 510 mV, a short-circuit current density Jsc of 2.41 mA, a fill factor FF of 0.49 and a power conversion efficiency η of 0.61% under AM 1.5 illumination. This result is interpreted in terms of minimization of the charge transfer resistance. The performance will drop for further deposition because the charge transfer resistance will increase due to QDs agglomeration.